In my U.S. Pat. No. 4,483,168 which was issued on Nov. 20, 1984, I disclosed new and useful apparatus for forming shaped pieces. One embodiment of that invention which is particularly useful in forming metal parts such as the vanes used in the compressor section of gas turbines, comprises apparatus which includes a flat surfaced die element which includes a workpiece forming depression in or as part of its upper surface. A pair of yoke-mounted cylindrical rolls, oriented with their axes parallel and positioned one above the other, are located between the flat, upper surface of the die element and the flat lower surface of a downward acting roll platen element that is actuated into its backing position and held there by a vertically oriented hydraulic press. The rolls are simultaneously moveable horizontally by means of a horizontally oriented hydraulic ram, the piston rod of which acts upon the yoke mounting of the rolls, while the rolls are in rolling contact with each other and with the upper surface of the die element and the lower surface of the top, roll platen element. By this means, forming stock from which desired vanes or other pieces are to be formed may be retentivity positioned at the location of the depression in the upper surface of the die element while the rolls, while under downward pressure from the vertically oriented hydraulic press acting via the roll platen element, are moved laterally by the horizontally oriented hydraulic ram. By performing one or more successive passes on the work piece, it is possible with this apparatus to form very hard materials into complex, intricate and precise shapes at much lower cost than was possible with the machining techniques previously utilized.
One of the characteristics of this apparatus is that the downward pressure brought to bear on the work piece by the roll set is imparted by the downward thrust of the vertical hydraulic press. As described in my above-referenced prior patent, if the resistance of the work piece to being formed exceeds that applied pressure, the piston of the vertical hydraulic press will be moved upward as the roll set moves across the workpiece. This can have the effect of causing the workpiece not to conform to the required or ultimately desired size and/or shape specifications. While this feature may be advantageous in many applications, in other situations this can be an undesirable effect. For example, as materials typically used to form certain workpieces are of increased resistance to roll formation, the amount of pressure required to resist deflection of the roll set may be much higher than the press is capable of imparting. Therefore the technical difficulties attendant such increasingly high pressure hydraulic equipment may increase radically. Further, localized hard or less malleable areas in the work pieces can produce intolerable deviations in the work piece from applicable specifications.
Thus, in some situations it is desired in performing the forming passes for the vertical position of the rolls vis-a-vis the forming die element not to change substantially, to make it possible for each piece to be formed in a reduced number of passes, and/or to ensure that each piece conforms within acceptable tolerances to applicable dimensional specifications, such as local deviations due to localized changes in resistance to being formed. Further, it is sometimes the case that to maintain the very high pressures that are necessary to form pieces, particularly those made from materials having the reduced malleability that characterizes some of the work stock that is used in such technically difficult applications as turbine vanes, involves imposing stresses on the associated hydraulic equipment that may be so high as to be impractical or intolerable.
Therefore it has been found that in certain applications of this type of equipment, it is acceptable and desirable to fix more or less unyieldingly the position of the roll platen element while the workpiece is being formed, and to do so without having to use hydraulic pressure as the means for maintaining those relationships. It is preferable for this to be done by eliminating the necessity for using such hydraulic equipment altogether to hold the roll platen element and the die element in desired juxtaposition with respect to each other. At the same time, provision must be made for getting at the forming area easily, for such purposes as to install work piece forming stock, to remove workpieces and debris, to change die members, to maintain the equipment, etc.
Accordingly, it is an object of this invention to provide means useful in the roll-forming of objects in desired shapes and dimensions.
Another object of this invention is to provide means which will satisfy the foregoing objective while assuring that deviations from design specifications of the objects so formed will remain within tolerable levels.
Still another object of this invention is to provide means for satisfying one or more of the foregoing objectives while reducing the amount of work necessary during forming operations.
Yet another object of this invention is to provide means for satisfying one or more of the foregoing objectives in which a hydraulic mechanism to maintain vertical closure pressure on the roll platen element is not necessary.